March 28, 2009

The Brain in Middle World

This is part 2 of 5 in the series Brain - Time - Music - Computing.
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Even though perpetual contingency characterizes Middle World, the underlying dynamics are not random. On the contrary, their complexity thinly veils a rich variety of spatio-temporal patterns [4]. The term pattern, here, denotes “a regular and intelligible form or sequence discernible in certain actions or situations; esp. one on which the prediction of successive or future events may be based” (Oxford English Dictionary). Under such conditions, the brain has evolved into a highly effective spatio-temporal pattern detection and prediction system [2]. Moreover, the brain exhibits an “infovorous” behavior [1]: it craves for new experiences. More specifically, studies have linked sensory novelty and surprise to pleasure and reward activity in the brain. This is consistent with the continuous refinement of the prediction system through acquisition of new knowledge.

Both the creation and performance of music play directly into these fundamental brain mechanisms [3], taking advantage of the pleasure systems wired in the brain. From rhythmic patterns to more intangible tonality systems, the brain naturally picks-up, processes, and responds to, spatio-temporal structures in music. If too predictable, a piece of music or a performance are simply boring; on the other hand, the listener might not be able to make sense of a piece or a performance that is "too" unexpected. The art of creating music, or any other artifact intended to stimulate human interest, hinges on striking a delicate balance between familiarity and surprise; establishing a frame of anticipation, and venturing outside of this frame in such a way that prompts the listener to adapt her own frame of reference.

These observations point to a highly dynamic notion of music making and listening. If the musical expertise, and expectations, of brains change every time they experience music, then what constitutes interesting music and interesting performance changes constantly, both at the individual and at the cultural levels. The computational modeling of such concepts as musical appreciation must therefore characterize how context, both individual and collective, plays out in the dynamics of the particular perceptual and cognitive processes involved.

References
[1] I. Biederman and E. A. Vessel. Perceptual pleasure and the brain. American Scientist, 94:249–255, 2006.
[2] Jeff Hawkins and Sandra Blakeslee. On Intelligence. Times Books, 2004.
[3] David Huron. Sweet Anticipation: Music and the Psychology of Expectation. MIT
Press, 2006.
[4] Ken Richardson. A Mind for Structure: Exploring the Roots of Intelligent Systems.
Brown Walker Press, 2006.

March 18, 2009

Middle World

This is part 1 of 5 in the series Brain - Time - Music - Computing.
Next: The Brain in Middle World

Dawkins remarks that brains have evolved to help animals survive within the orders of magnitude of size and speed at which their bodies operate. He calls Middle World (MW) this relatively narrow range of phenomena directly and intuitively accessible to perceptual and cognitive processes [2]. Dawkins invokes the human brain’s evolutionary entanglement with MW to explain humans' difficulty in grasping, and coping with, the physical realities of the universe outside of its familiar confines, from the sub-atomic scales of quantum physics to the universe-size scales of relativity. But the fundamental properties of MW can also help characterize the nature of the tasks at which brains came to excel, in particular the fundamentally dynamic nature of these tasks.

Everything in MW is subject to what the human brain perceives and understands as time, “the continuum of experience in which events pass from the future through the present to the past” (Wordnet). MW time (MWT) cannot be altered in any way: in particular, its flow cannot be slowed, stopped or reversed. The implications are deep. First, nothing in MW can ever happen again, every and any experience is that of an ever changing environment, by an ever changing observer. Exact reproduction of an experience, such as a musical performance, is a practical impossibility both for the performer and for the listener. Second, mathematical abstractions, such as randomness, synchrony, or infinity, do not exist in MW (David Cope discusses randomness in [1]). Mathematics define an idealized world of spatio-temporal invariants, which in some respects models aspects of MW, and aspects of the universe outside of MW that are difficult for MW-evolved brains to grasp.

Mathematics provide a framework for MW brains to characterize and manipulate invariants in a way that is consistent, completely and absolutely predictable, independent of time and space; in particular, these invariants are not sub ject to, and allow the abstraction of, the flow of MWT. The theory of computation came about to formalize actions and operations in the mathematical world, where they must abide by the principles of consistency, predictability, universality. This requires not only that the notion of time be abstracted, but also that the resulting abstract manifestation of time in computing be enforced as a strong invariant. The mathematical properties of computation, especially the abstraction and immutable crystallization of the flow of time, constitute major obstacles to the useful computational modeling of many important MW phenomena.

References
[1] David Cope. Computer Models of Musical Creativity. MIT Press, 2005.
[2] Richard Dawkins. The God Delusion. Houghton Mifflin Harcourt, 2006. See also Dawkins' TED Talk: The Universe Is Queerer Than We Can Suppose

March 08, 2009

Brain - Time - Music - Computing

The next 5 posts are excerpts from a chapter, titled "Time and Perception in Music and Computation," which appears in the book New Computational Paradigms for Computer Music, pp.125-146.

The Oxford English Dictionary defines music as “the art or science of combining vocal or instrumental sounds to produce beauty of form, harmony, melody, rhythm, expressive content, etc.” Composers and performers of music invent and produce sounds, carefully organized with the intent and purpose to trigger emotional responses from the listeners, usually humans. Creating music therefore involves deep understanding and mastery, whether intuitive of explicit, of the human auditory perceptual and cognitive apparatus.

A reflexion on the nature of the phenomena involved points towards the ability of the mind to move in and out of flows of time, real or imaginary, as a defining feature of perceptual and cognitive activities. A comprehensive computational paradigm for computer music must afford the modeling of this ability.

Part 1: Middle World
Part 2: The Brain in Middle World
Part 3: Time and Perception
Part 4: Time and the Brain
Part 5: Time in Computation